Boris Johnson was accused of telling “outright lies” by an American reporter on Tuesday, as he endured an awkward press conference with US Secretary of State John Kerry.

Kerry praised the new foreign secretary as a man of “considerable intellect” who appeared to be “a very smart and capable man”.

However the US media which had travelled to London with Kerry were less kind - grilling Johnson on his past comments about US politicians including branding Hillary Clinton a “sadistic nurse” and President Obama “part-Kenyan”.

Gardiner Harris, of the New York Times, asked Johnson: “I understand you don’t want to revisit the past, but you have an unusually long history of wild exaggerations and frankly outright lies, which I think few foreign secretaries have prior to this job.

Harris asked how Kerry “should believe” anything Johnson said in his new job.

Johnson, who hung his head briefly as some of his past words were read back to him, said “people are more than welcome to rake over stuff I have written over many, many years”.

Asked whether he wanted to apologise to world leaders he had offended in various newspaper columns, Boris insisted his remarks were often taken out of context.

“I’m afraid there is such a rich thesaurus of things I’ve said that have been, one way or another, through what alchemy I do not know, somehow misconstrued, that it would really take me too long to enface in a full global itinerary of apology,” he said.

“People who read the things in their proper context can understand what was intended.”

Boris Johnson: “We can spend an awfully long time going over lots of stuff I have written over the last 30 years" https://t.co/1g8N0YH90D

Kerry used the press conference to praise Boris as “fully prepared” to be foreign secretary. “This man is a very smart and capable man,” he told Johnson.

Johnson replied with a sigh of relief: “I can live with that.” Reaching over to the foreign secretary, Kerry told him: “It’s called diplomacy.”

During the EU referendum campaign, Johnson triggered an outcry after he suggested President Obama’s “part-Kenyan” heritage meant he could have an “ancestral dislike” of the British.

Obama was visiting London at the time to urge the UK to remain inside the EU.

And in a 2007 Daily Telegraph column, Johnson described Clinton someone with “dyed blonde hair and pouty lips, and a steely blue stare, like a sadistic nurse in a mental hospital”.

Another US journalist today asked Johnson whether he took those comments back or if he wanted to “take them with you into your new job as some sort of indicator as the type of diplomacy you will practice”.

In a sign of perhaps how Johnson is viewed in the United States, a State Department official struggled to keep a straight face when told Johnson had been appointed foreign secretary.

Earlier today, Kerry’s visit to London hit a bump when he sharply knocked his head against the door of No.10 Downing Street by accident.